PROJECT SUMMARY Embolization is an effective, minimally invasive technique to control the flow of blood in the body. This procedure is used to treat many conditions including: tumors, aneurysms and arteriovenous malformations. Currently, no inherent radiopaque temporary embolic agents are available in the clinic that allows direct imaging of the material during the procedure and during follow up treatments. An ideal agent would combine the visibility of contrast agents, have the shape-ability and versatility of Gelfoam, and still maintain its efficacy to stop blood flow in the target tissue without causing irreversible ischemia in the process. It would allow the physician direct visualization of the actual plug without the need for accompanying contrast. More precise placement and faster procedures could result from improved visualization of a Gelfoam like agent. We propose to develop and optimize a translatable, radiopaque temporary embolic agent and characterize its? physico-chemical and biological properties followed by a proof-concept in vivo pilot study. Further development of these agents for temporary embolization procedures will also require understanding of their degradation behavior and hemostatic ability. This project will address the challenge associated with identifying the location of Gelfoam when it is used as a temporary embolic. A radiopaque embolization agent could reduce repeated radiation exposure to the patient, the physician and staff and may also allow subsequent imaging of treated areas of concern with less imaging artifact from permanent metallic plugs. The major innovation of this proposal is the development of a radiopaque temporary embolic. Existing injectable embolic agents (e.g. Gelfoam) integrated with X-ray absorbing contrast agents (e.g., iohexol) can easily meet all the clinical requirements of efficient delivery to target arteries, rapid setting process without adhesion to catheters, good visibility by x-ray imaging and efficient embolization results.